scholarly journals A Differential Refractometer of High Sensitivity

1955 ◽  
Vol 8 (2) ◽  
pp. 212 ◽  
Author(s):  
PG Guest
Keyword(s):  
Brightness Temperature ◽  
Graphical Method ◽  
High Sensitivity ◽  
Smoothing Effect ◽  
Differential Refractometer

A graphical method is given for correcting the smoothing effect which arises when a celestial distribution of brightness temperature is scanned with an aerial beam. The method is much simpler to apply than previous methods which have been used and is no l

scholarly journals Chord Construction for Correcting Aerial Smoothing

1955 ◽  
Vol 8 (2) ◽  
pp. 200 ◽  
Author(s):  
RN Bracewell
Keyword(s):  
Brightness Temperature ◽  
Graphical Method ◽  
Smoothing Effect

A graphical method is given for correcting the smoothing effect which arises when a celestial distribution of brightness temperature is scanned with an aerial beam. The method is much simpler to apply than previous methods which have been used and is no less accurate.

Biological Systems to Assay Herbicidal Bleaching

1979 ◽  
Vol 34 (11) ◽  
pp. 1044-1046 ◽  
Author(s):  
Gerhard Sandmann ◽  
Karl-Josef Kunert ◽  
Peter Böger
Keyword(s):  
Graphical Method ◽  
Algal Cell ◽  
Biological Systems ◽  
High Sensitivity ◽  
Phycomyces Blakesleeanus ◽  
Dixon Plot ◽  
Physiological Conditions ◽  
Scenedesmus Acutus ◽  
Subsequent Application

Abstract Two strains of Scenedesmus acutus were found useful to study the influence of bleaching agents on either the greening process or the fully pigmented algal cell during growth. Both physiological conditions exhibit high sensitivity to bleaching herbicides. With this new assay, contrasting bleach­ing effects with the same compound can be found allowing differentiation of the herbicidal action of bleaching agents which apparently is a multifunctional one. Furthermore, the I50 can be determined rather rapidly in a simple graphical method by a Dixon plot. A subsequent application of bleaching herbicides to cultures of the fungus Phycomyces blakesleeanus rules out a possible specific action of the compounds assayed on chlorophyll or photosynthetic redox carriers. This latter assay can show whether or not the herbicides synthesis as is the case with difunon or SAN 9789.

scholarly journals Influence of meter-scale wind-formed features on the variability of the microwave brightness temperature around Dome C in Antarctica

2013 ◽  
Vol 7 (4) ◽  
pp. 3675-3716 ◽  
Author(s):  
G. Picard ◽  
A. Royer ◽  
L. Arnaud ◽  
M. Fily
Keyword(s):  
Numerical Simulations ◽  
Brightness Temperature ◽  
High Sensitivity ◽  
Microwave Emission ◽  
Emission Model ◽  
Density Profiles ◽  
Microwave Brightness Temperature ◽  
Snow Properties ◽  
The Difference ◽  
Microwave Radiometers

Abstract. Space-borne passive microwave radiometers are widely used to retrieve information in snowy regions by exploiting the high sensitivity of microwave emission to snow properties. For the Antarctic Plateau, many studies presenting retrieval algorithms or numerical simulations have assumed, explicitly or not, that the subpixel-scale heterogeneity is negligible and that the retrieved properties were representative of whole pixels. In this paper, we investigate the spatial variations of brightness temperature over a range of a few kilometers in the Dome C area. Using ground-based radiometers towed by a vehicle allowing measurements with meter resolution, we collected brightness temperature transects at 11, 19 and 37 GHz at horizontal and vertical polarizations. The most remarkable observation was a series of regular undulations of the signal with a significant amplitude of up to 10 K at 37 GHz and a quasi-period of 30–50 m. In contrast, the variability at longer length scales seemed to be weak in the investigated area and the mean brightness temperature was close to AMSR-E and WindSat satellite observations for all the frequencies and polarisations. To establish a link between the snow characteristics and undulation-scale variations of microwave emission, we collected detailed snow grain size and density profiles to run the DMRT-ML microwave emission model at two points where opposite extrema of brightness temperature were observed. The numerical simulations revealed that the difference in density of the upper first meter of the snowpack explained most of the brightness temperature variations. In addition, we found in the field that these variations of density were linked to the hardness of the snowpack. Areas of hard snow – probably formed by the wind – were clearly visible and covered as much as 39% of the investigated area. Their brightness temperature was higher than in normal areas. This result implied that the microwave emission measured by satellites over Dome C is more complex than expected and very likely depends on the areal proportion of the two different types of areas having distinct snow properties.

scholarly journals Planetary Nebulae: Advances in Radio Observations

1978 ◽  
Vol 76 ◽  
pp. 111-120 ◽  
Author(s):  
Yervant Terzian
Keyword(s):  
Brightness Temperature ◽  
Planetary Nebulae ◽  
High Sensitivity ◽  
Aperture Synthesis ◽  
Collisional Broadening ◽  
Temperature Distributions ◽  
Ngc 7027 ◽  
5 Ghz ◽  
Unambiguous Detection ◽  
Co Emission

The most recent review on planetary nebulae at radio wavelengths appeared in 1974 by Thompson. Previous summaries were given by Terzian (1968) and Higgs (1973). Major advances in this subject include extensive continuum observations at 5 GHz of southern planetary nebulae; the highly successful aperture synthesis observations providing brightness temperature distributions with a resolution of a few arc seconds; the high sensitivity observations of radio recombination lines which have allowed the unambiguous detection of collisional broadening in NGC 7027; the very recent detection of molecular CO emission from NGC 7027, IC 418 and NGC 6543, and CO and OH emission from possible proto-planetary nebulae.

scholarly journals Influence of meter-scale wind-formed features on the variability of the microwave brightness temperature around Dome C in Antarctica

2014 ◽  
Vol 8 (3) ◽  
pp. 1105-1119 ◽  
Author(s):  
G. Picard ◽  
A. Royer ◽  
L. Arnaud ◽  
M. Fily
Keyword(s):  
Numerical Simulations ◽  
Brightness Temperature ◽  
High Sensitivity ◽  
Microwave Emission ◽  
Emission Model ◽  
Density Profiles ◽  
Microwave Brightness Temperature ◽  
Snow Properties ◽  
The Difference ◽  
Microwave Radiometers

Abstract. Space-borne passive microwave radiometers are widely used to retrieve information in snowy regions by exploiting the high sensitivity of microwave emission to snow properties. For the Antarctic Plateau, many studies presenting retrieval algorithms or numerical simulations have assumed, explicitly or not, that the subpixel-scale heterogeneity is negligible and that the retrieved properties were representative of whole pixels. In this paper, we investigate the spatial variations of brightness temperature over a range of a few kilometers in the Dome C area. Using ground-based radiometers towed by a vehicle, we collected brightness temperature at 11, 19 and 37 GHz at horizontal and vertical polarizations along transects with meter resolution. The most remarkable observation was a series of regular undulations of the signal with a significant amplitude reaching 10 K at 37 GHz and a quasi-period of 30–50 m. In contrast, the variability at longer length scales seemed to be weak in the investigated area, and the mean brightness temperature was close to SSM/I and WindSat satellite observations for all the frequencies and polarizations. To establish a link between the snow characteristics and the microwave emission undulations, we collected detailed snow grain size and density profiles at two points where opposite extrema of brightness temperature were observed. Numerical simulations with the DMRT-ML microwave emission model revealed that the difference in density in the upper first meter explained most of the brightness temperature variations. In addition, we found that these variations of density near the surface were linked to snow hardness. Patches of hard snow – probably formed by wind compaction – were clearly visible and covered as much as 39% of the investigated area. Their brightness temperature was higher than in normal areas. This result implies that the microwave emission measured by satellites over Dome C is more complex than expected and very likely depends on the year-to-year areal proportion of the two different types of snow.

Radio Measurements of Coronal Magnetic Fields

1994 ◽  
Vol 144 ◽  
pp. 21-28 ◽  
Author(s):  
G. B. Gelfreikh
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Transverse Magnetic ◽  
Radio Sources ◽  
Radio Waves ◽  
Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

Backscattered Electron Imaging of GaAs/AlGaAs Super Lattice Structures with an Ultra-High- Resolution SEM

1988 ◽  
Vol 46 ◽  
pp. 204-205
Author(s):  
Kazumichi Ogura ◽  
Michael M. Kersker
Keyword(s):  
High Resolution ◽  
Layer Structure ◽  
High Sensitivity ◽  
Beam Current ◽  
Electron Beam Current ◽  
Lattice Structures ◽  
Super Lattice ◽  
Different Types ◽  
Backscattered Electron ◽  
Electron Imaging

Backscattered electron (BE) images of GaAs/AlGaAs super lattice structures were observed with an ultra high resolution (UHR) SEM JSM-890 with an ultra high sensitivity BE detector. Three different types of super lattice structures of GaAs/AlGaAs were examined. Each GaAs/AlGaAs wafer was cleaved by a razor after it was heated for approximately 1 minute and its crosssectional plane was observed.First, a multi-layer structure of GaAs (100nm)/AlGaAs (lOOnm) where A1 content was successively changed from 0.4 to 0.03 was observed. Figures 1 (a) and (b) are BE images taken at an accelerating voltage of 15kV with an electron beam current of 20pA. Figure 1 (c) is a sketch of this multi-layer structure corresponding to the BE images. The various layers are clearly observed. The differences in A1 content between A1 0.35 Ga 0.65 As, A1 0.4 Ga 0.6 As, and A1 0.31 Ga 0.69 As were clearly observed in the contrast of the BE image.

An x-ray microprobe based upon a close-coupled focal-spot / glass capillary arrangement

1992 ◽  
Vol 50 (2) ◽  
pp. 1758-1759
Author(s):  
D. A. Carpenter ◽  
M. A. Taylor
Keyword(s):  
Imaging Techniques ◽  
Fluorescence Analysis ◽  
High Sensitivity ◽  
Specimen Preparation ◽  
X Rays ◽  
Glass Capillary ◽  
Close Coupling ◽  
X Ray ◽  
Point To Point ◽  
Beam Damage

The development of intense sources of x rays has led to renewed interest in the use of microbeams of x rays in x-ray fluorescence analysis. Sparks pointed out that the use of x rays as a probe offered the advantages of high sensitivity, low detection limits, low beam damage, and large penetration depths with minimal specimen preparation or perturbation. In addition, the option of air operation provided special advantages for examination of hydrated systems or for nondestructive microanalysis of large specimens.The disadvantages of synchrotron sources prompted the development of laboratory-based instrumentation with various schemes to maximize the beam flux while maintaining small point-to-point resolution. Nichols and Ryon developed a microprobe using a rotating anode source and a modified microdiffractometer. Cross and Wherry showed that by close-coupling the x-ray source, specimen, and detector, good intensities could be obtained for beam sizes between 30 and 100μm. More importantly, both groups combined specimen scanning with modern imaging techniques for rapid element mapping.

Ultrastructural identification of three types of sensory setae on copepod antennae

1995 ◽  
Vol 53 ◽  
pp. 956-957
Author(s):  
T. M. Weatherby ◽  
P.H. Lenz
Keyword(s):  
Phase Locking ◽  
Membrane Surface ◽  
Reaction Times ◽  
High Sensitivity ◽  
Structural Features ◽  
Calanoid Copepods ◽  
Marine Food Webs ◽  
Dendritic Membrane ◽  
Ultrastructural Characterization

Crustaceans, as well as other arthropods, are covered with sensory setae and hairs, including mechanoand chemosensory sensillae with a ciliary origin. Calanoid copepods are small planktonic crustaceans forming a major link in marine food webs. In conjunction with behavioral and physiological studies of the antennae of calanoids, we undertook the ultrastructural characterization of sensory setae on the antennae of Pleuromamma xiphias.Distal mechanoreceptive setae exhibit exceptional behavioral and physiological performance characteristics: high sensitivity (<10 nm displacements), fast reaction times (<1 msec latency) and phase locking to high frequencies (1-2 kHz). Unusual structural features of the mechanoreceptors are likely to be related to their physiological sensitivity. These features include a large number (up to 3000) of microtubules in each sensory cell dendrite, arising from or anchored to electron dense rods associated with the ciliary basal body microtubule doublets. The microtubules are arranged in a regular array, with bridges between and within rows. These bundles of microtubules extend far into each mechanoreceptive seta and terminate in a staggered fashion along the dendritic membrane, contacting a large membrane surface area and providing a large potential site of mechanotransduction.

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